Hi guys. My car is a 1990 911 Carrera 4.

Long story short, my blower motor is making a ton of noise and I pulled the fuse. I'm wondering if it's safe to drive it while I figure out what to do and get it fixed?? I read somewhere that the blower also helps to cool the motor. Is that true or mixing my Carrera 4 with the turbo?

Long story:

When I bought my car, the rear heater blower didn't work. I didn't notice until after I paid and was on my way home. My bad. I used the list to find a blown fuse and replaced it. Wa Laa. Blower worked. But later found I no heat from it. I've been doing the research on here and was about to dive in and tackle it in the next couple of days, but yesterday I noticed the engine bay was VERY noisy. Sure enough, it was the blower. So I pulled the fuse.

It looks like I might need to replace the motor. I don't have much for tools here and just bought and moved onto a sailboat, so it's hard to work on this myself as I no longer have a garage, but I'm also not keen on taking it back to the mechanic. I already spent $2000 to fix a leak and there is still a leak!

I'm hoping I can do this myself and save some $$$...and eventually get back some heat in the process.

 

Unless it's a super hot summer's day (and you've been sitting in traffic or something) the blower function where it cools the headers isn't going to turn on anyway. What happens is that if it's super hot in there, the blower will come on for 20mins after shutoff. So I'd say you're ok to drive it, after pulling the 30A fuse for the blower.

There are a few threads for ditching the blower motor altogether and replacing it with a Carrera Cup heater bypass tube, which simplifies things a lot.

 

I have driven hard all day on the track in 35 C weather with no ill effects, despite having no blower fan. That also includes stopping for 20 - 30 minutes between track sessions so there was no airflow at all during those times.

Don't worry - just drive it.

Marc

 

Okay cool. I was so stressed about driving it. One other thing I notice is the boiling water type gurgling sound. The car has always done that and I've had no issues for the over 1000 miles I've put on it, and no signs of increasing temperatures. I guess with a cabriolet, it's easier to hear the working sounds of the motor and the fluids circulating.

I saw this thread about removing the blower assembly:

https://rennlist.com/forums/964-1989...resistors.html

I'm assuming that by doing that though you have no heat, correct? I'd like some heat. I froze my butt off last weekend after getting caught in a rainstorm and having to drive 1.5 hours on the freeway on a cool night. So if I get no heat, I'll try to fix the blower instead of stripping it, but it's nice to know I can drive the car for now. It gets hot in the valley, especially on the freeway, but I live in Marina Del Rey now, so it's not so bad while running around until I sort it out. Thanks guys.

 

Is this different than that little resistor mod in the DIY's? I didn't see a "bypass tube" in that description.

Also, I don't quite understand what the resistor does in that DIY? https://rennlist.com/forums/964-1989...resistors.html

 

The resistors fool the CCU and make it "think" it's all there working, so the system works fine. Though those resistors get VERY hot... and personally, I don' t want hot things in my engine-bay...!
There's another way to safely fool the CCU and make it work: have a look at post #79 here

When doing these mods, you probably removed the rear blower and installed a by-pass.

 

Check that thread too:
https://rennlist.com/forums/964-foru...ypass-box.html

You should not need the resistors if you disconnect the blower electrical connector (on the left side of the blower), and replace the blower relay in the engine bay fusebox by a jumper between 30 and 87.

And for the repair: http://www.911targa.net/Targa.net/Wo..._Motorraum.pdf

 

Doesn't the rear blower help (considerably) get air moving to the "suitcase" (central heating-AC chamber)
so the front fan(s)' work is easier? For those of you that have gone the bypass-tube route AND use your car for all-weather, everyday use, what "ballpark" percentage reduction in heating-air cond. power-comfort level would you estimate? I'm NOT a track guy, so am hesitant to follow suit. But if there is ONLY a slight reduction in efficiency AND a reduction of system complexity with NO ill effects, if my rear blower needs repl. I may go this route. Thanx for response(s)!

 

Hot air reduction is slight. Comfort level is more than sufficient, I'd say 70% (more than you' d need in freezing weather).

Do not go the jumper route, it may lead to battery-drain...

 

I have the heater bypass pipe in mine, and I followed Anto1150's advise on how to wire it up (by the way, thanks for the info), no drain on a 1991 (1990 Dec 14th build date), and as far as heat in the car, I can say I hardly noticed any difference, and I am in Canada.

 

I have the bypass, and I can't say I've noticed any loss of heat.

 

anto1150: what is this "jumper" route, and how does it differ from what babalouie, et. al. have done? Thanx. P.s., mine is a '91 (sept. 90 fab. date), if it is of any consequence.

 

When you put a jumper between 30 and 87 instead of the rear blower relay (see image of post of rollingjack page 2 of https://rennlist.com/forums/964-foru...***-box-2.html - there is also a second jumper 30c-87c which is useless on that picture), you send permanent 12V to the motor of the rear-blower OR the resistor replaces it. THIS causes battery drain because the resistor drains current even if the ignition is off.

Now, the 30-87 jumper also tells pin G19 of the Heating Airco control unit (on the dash) that the rear blower is running on high speed.

If you have disconnected the rear blower and have no resistor to replace it, the Heating Airco control unit will think that the rear blower is running on high speed all the time and you SHOULD not have a drain.

I will have to test it on my 90 sometimes. I just replaced the motor of the blower when it went bad.

 

The jumper method was originally suggested by RollinJack, but when some ppl said that it still led to a current drain, I came up with the relay idea, which was then refined by Anto1150 with the "wire to the coil" idea

 

The wire to coil is technically the best solution (don't forget the fuse though): No ignition, no 12V.
The jumper is neater: all remains in the fusebox.